In many applications, such as surveillance, military, detection, imagery, as well as others, it may be desirable to view multiple bands of the electromagnetic spectrum at the same time. Each band may provide some information about the scene that other bands cannot provided as easily. For example, the visible spectrum may be useful for providing an overall visual representation of a scene under good or relatively good lighting conditions. The millimeter (mm) wave band may be useful for providing a visual representation of a scene under long range or inclement weather conditions, as it may penetrate fog, rain and even opaque solids. The infrared band may be useful in determine temperature characteristics of an object in a scene. These are only a few examples. By viewing multiple bands of the electromagnetic spectrum at the same time, a viewer may be able to gain a better understanding of the scene.
Some existing systems capable of providing multiple band images optically separate the different wavelength bands, and process the bands separately, before combining the results to provide a multi-band scene. For example, and in some cases, a beam splitter or the like is used to optically separate the different bands into separate optical paths. In other cases, different bands of wavelengths are focused onto different focal planes, and separate detectors are provided at the different focal planes. In many of these cases, image processing is used to combine the information gained from the different bands into a common scene.